This application is based on patent application No. H11-219473 (219473/1999) filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a method of manufacturing a liquid crystal display element in which a liquid crystal material and spacer particles are disposed between substrates.
2. Description of the Background Art
In the field of electronic display devices, liquid crystal display elements have been developed for actual use in a wide range extending from a small information device terminal to a large projection display.
The liquid crystal display element is generally manufactured in such a manner that two glass substrates are fixed together to form a cell while keeping a gap between substrates with spacer particles, a liquid crystal material is filled into the space between the substrates through an inlet after fixing of the substrates, and flat plates are pressed against the substrates from both sides of the substrates to adjust the gap before closing the inlet.
A vacuum filling method is widely used as a method of filling the liquid crystal material into the cell. In the vacuum filling method, the cell provided at its end surface with the inlet is disposed in a vacuum tank, and the pressure in the vacuum tank is reduced to attain a vacuum state in the cells. Then, a liquid crystal material already subjected to vacuum degassing is brought into contact with the inlet within the vacuum tank, and then the pressure outside the cell is restored to an atmospheric pressure so that the cell is filled with the liquid crystal material by the pressure difference.
In recent years, a liquid crystal display element using a film substrate has attracted attention because it allows reduction in thickness of the element itself.
However, the foregoing vacuum filling method, which is used for the cell employing the glass substrates, requires a long time for discharging the air from the cell and for filling the liquid crystal material thereinto, and therefore suffers from a problem of low productivity. In particular, this problem becomes remarkable in the structure using large substrates. Such a problem also arises that an unnecessary liquid crystal material adheres to the cell end surface, resulting in a large loss of the liquid crystal material. Further, when producing a plurality of the liquid crystal display element, a plurality of the inlet of the cell are brought into contact with the liquid crystal material in a reservoir, and thereby a plurality of cells are immersed several or many times in the liquid crystal material in the reservoir, and resulting in that the liquid crystal material in the reservoir is polluted.
If the liquid crystal display element using the film substrate is produced with the vacuum filling method, both the operations of discharging the gas and filling the liquid crystal material require more time than those for the display element using the glass substrates, because the film substrate has flexibility. In particular, this problem becomes remarkable when both of the substrates are the film substrates.
Therefore, such a method has been proposed that the film substrate is temporarily fixed to a glass substrate or the like for forming the cells, and then the liquid crystal material is filled thereto. However, this method requires complicated operations for fixing the film substrate to the glass substrate, and removing it from the glass after filling the liquid crystal material. Further, the film substrate may be damaged or deformed. It is also necessary to set the optimum conditions for fixing the film substrate to the glass substrate. Problems other than the above may also arise. In the above method of fixing the film substrate to the glass for manufacturing the liquid crystal display element, increase in number of steps as well as complication thereof are unavoidable, and the larger size of the substrate makes the manufacturing more difficult.
For good display, the thickness of the liquid crystal material must be constant in each portion of the liquid crystal display element. For this, the liquid crystal display element is generally provided with spacer particles located between the substrates for controlling the distance (gap) between the substrates holding the liquid crystal material therebetween, and thereby for keeping the constant thickness of the liquid crystal material in each portion. However, these manners cannot yet sufficiently achieve the uniformity in gap between the substrates, and therefore the uniformity in thickness of the liquid crystal material.
An object of the invention is to provide a novel method of manufacturing a liquid crystal display element provided with spacer particles and a liquid crystal material disposed between a pair of substrates.
More specifically, an object of the invention is to provide a method of manufacturing a liquid crystal display element, which achieves simple manufacturing steps, short manufacturing time and high productivity.
Another object of the invention is to provide a method of manufacturing a liquid crystal display element, which achieves simple manufacturing steps, short manufacturing time, high productivity and sufficient uniformity in distance (gap) between the substrates.
Still another object of the invention is to provide a method of manufacturing a liquid crystal display element, which achieves simple manufacturing steps, short manufacturing time, high productivity and sufficient suppression of occurrence of bubbling between the substrates.
The invention provides a method of manufacturing a liquid crystal display element provided with spacer particles and a liquid crystal material disposed between first and second substrates.
The method of manufacturing a liquid crystal display element according to the invention essentially comprising:
an adhesive material disposing step of disposing an adhesive material on a predetermined portion of at least one of the first and second substrates;
a spacer particle disposing step of disposing the spacer particles on at least one of the first and second substrates;
a liquid crystal material supplying step of supplying the liquid crystal material onto a predetermined portion of at least one of the first and second substrates; and
a substrate fixing step of fixing the first and second substrates together with the adhesive material, the spacer particles and the liquid crystal material therebetween.
In the method of manufacturing a liquid crystal display element according to the invention, a flexible substrate is used for at least one of the first and second substrates.
In an aspect of the method of manufacturing the liquid crystal display element according to the invention, the substrate fixing step is performed in such a manner that the first and second substrates are fixed together by applying a pressure to the first and second substrates from an end portion toward the other end portion thereof under a condition that an impulse F applied to each of the spacer particles is in a range from 0.001 gfxc2x7sec to 0.1 gfxc2x7sec.
In another aspect of the method of manufacturing the liquid crystal display element according to the invention, the substrate fixing step is performed in such a manner that the first and second substrates are fixed together by applying a pressure and a heat to the first and second substrates from an end portion toward the other end portion thereof; and
a parameter X relating to the heating in the substrate fixing step satisfies a relationship of 200xe2x89xa6Xxe2x89xa63000, where X=(Txe2x88x9220)/(Vxc2x7D), T is a heating temperature (xc2x0C.), V is a fixing speed (mm/sec) of the first and second substrates, and D is a diameter of the spacer particle (mm).
In still another aspect of the method of manufacturing the liquid crystal display element according to the invention, the substrate fixing step is performed in such a manner that the first and second substrates are fixed together by applying a pressure to the first and second substrates from an end portion toward the other end portion thereof; and
the spacer particle disposing step is performed to dispose the spacer particles such that the spacer particles, to be located between the first and second substrates in the substrate fixing step, occupy an area at a ratio S of 0.003 or more to a unit area of the substrate.
In any of the above mentioned manufacturing methods, some of the steps may be executed simultaneously. For instance, the adhesive material disposing step and the spacer particle disposing step may be executed simultaneously by adding the spacer particles in the adhesive material before disposing the adhesive material and spacer particles to at least one of the first and second substrates. Alternatively or in addition, the spacer particle disposing step may be simultaneously executed with the liquid crystal material supplying step by adding the spacer particles in the liquid crystal material before performing these steps. As to the liquid crystal supplying step, this step may be executed before or during the substrate fixing step.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.